1. Field of the Invention
The present invention relates to an electric device and a printing apparatus using the same and, particularly, to an electric device including, for example, a plurality of LED lamps and a plurality of switches, and a printing apparatus using the same as part of an operation unit.
2. Description of the Related Art
Operation units of various information processing apparatuses are provided with electric devices each including, for example, switches to be operated by the user, and LED lamps which notify the user of the apparatus operation states.
Japanese Patent Laid-Open No. 2008-033915, for example, discloses a printing apparatus which prints on a print medium using a printhead, and its operation unit uses an electric device formed by an LED lamp and switch as well. Such an electric device normally has a plurality of LED lamps and a plurality of switches, which are controlled by, for example, a microcomputer.
For this control operation, the electric device separately includes input ports which input instructions from the plurality of switches, and output ports which output driving signals to turn on the plurality of LED lamps. Also, input/output signal lines for the plurality of switches and plurality of LED lamps constitute a matrix, which is controlled by the microcomputer. That is, in this control operation, signal lines used for instructions input from the plurality of switches, and those used to drive the LED lamps are shared to time-divisionally control the timings of instructions input from the plurality of switches, and the timings of output of driving signals to drive the LED lamps.
However, in a configuration as in the above-mentioned conventional technique, it is necessary to switch between port input and output at high speed to independently perform LED light emission control and switch input instruction detection control, thus requiring a dedicated logic circuit. Also, this configuration must not only be separately provided with dedicated input and output ports, but also be provided with dedicated signal lines, thus increasing the circuit scale. This raises the manufacturing cost of an electric device including a plurality of LED lamps and a plurality of switches.
Also, in the configuration of the above-mentioned conventional technique, because the LEDs are time-divisionally driven is performed, light emission control of the LEDs cannot be done for a sufficient time, thus lowering the brightnesses of the LEDs. Normally, when an operation unit of an information processing apparatus includes a plurality of LED lamps, the LED lamps desirably have uniform brightnesses in their light emission. It is therefore desirable to perform fine light emission control so as to uniform the light emission brightnesses of the plurality of lamps as much as possible.
In addition, an LED lamp built into an operation unit of an information processing apparatus is often required to provide brightness gradation in a plurality of levels. When, for example, an LED lamp notifies the user of information concerning the ink residual amount in an ink tank in an operation unit of an inkjet printing apparatus, it may be desirable to perform control so as to change the brightness in the following situation. For example, the light emission brightness of the LED lamp is changed to a low brightness if the replacement of the ink tank is desirable as the ink residual amount has become small, and to a high brightness if the replacement of the ink tank is urgent as the ink is exhausted.